R. Granier de Cassagnac

The centrality dependence of transverse momentum distributions and yields for ± , K ± , p, and p ¯in Au + Au collisions at ͱ s NN = 200 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider.We observe a clear particle mass dependence of the shapes of transverse momentum spectra in central collisions below ϳ2 GeV/ c in p T .Both mean transverse momenta and particle yields per participant pair increase from peripheral to midcentral and saturate at the most central collisions for all particle species.We also measure particle ratios of -/ + , K -/ K + , p ¯/ p, K / , p / , and p ¯/ as a function of p T and collision centrality.The ratios of equal mass particle yields are independent of p T and centrality within the experimental uncertainties.In central collisions at intermediate transverse momenta ϳ1.5-

The anisotropy parameter (v(2)), the second harmonic of the azimuthal particle distribution, has been measured with the PHENIX detector in Au+Au collisions at sqrt[s(NN)]=200 GeV for identified and inclusive charged particle production at central rapidities (|eta|<0.35) with respect to the reaction plane defined at high rapidities (|eta|=3-4 ). We observe that the v(2) of mesons falls below that of (anti)baryons for p(T)>2 GeV/c, in marked contrast to the predictions of a hydrodynamical model. A quark-coalescence model is also investigated.

Transverse momentum spectra of neutral pions in the range 1 &lt; p_T &lt; 10 GeV/c have been measured at mid-rapidity by the PHENIX experiment at RHIC in Au+Au collisions at sqrt(s_NN) = 200 GeV. The pi^0 multiplicity in central reactions is significantly below the yields measured at the same sqrt(s_NN) in peripheral Au+Au and p+p reactions scaled by the number of nucleon-nucleon collisions. For the most central bin, the suppression factor is ~2.5 at p_T = 2 GeV/c and increases to ~4-5 at p_T ~= 4 GeV/c. At larger p_T, the suppression remains constant within errors. The deficit is already apparent in semi-peripheral reactions and increases smoothly with centrality.

This report reviews the study of open heavy-flavour and quarkonium production in high-energy hadronic collisions, as tools to investigate fundamental aspects of Quantum Chromodynamics, from the proton and nucleus structure at high energy to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is given to the lessons learnt from LHC Run 1 results, which are reviewed in a global picture with the results from SPS and RHIC at lower energies, as well as to the questions to be addressed in the future. The report covers heavy flavour and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus collisions. This includes discussion of the effects of hot and cold strongly interacting matter, quarkonium photo-production in nucleus-nucleus collisions and perspectives on the study of heavy flavour and quarkonium with upgrades of existing experiments and new experiments. The report results from the activity of the SaporeGravis network of the I3 Hadron Physics programme of the European Union 7th Framework Programme.

Transverse momentum spectra of charged hadrons with p T < 8 GeV=c and neutral pions with p T < 10 GeV=c have been measured at midrapidity by the PHENIX experiment at BNL RHIC in d Au collisions at s NN p 200 GeV.The measured yields are compared to those in p p collisions at the same s NN p scaled up by the number of underlying nucleon-nucleon collisions in d Au.The yield ratio does not show the suppression observed in central Au Au collisions at RHIC.Instead, there is a small enhancement in the yield of high momentum particles.

Flow coefficients v_n for n = 2, 3, 4, characterizing the anisotropic collective flow in Au+Au collisions at sqrt(s_NN) = 200 GeV, are measured relative to event planes \Psi_n determined at large rapidity. We report v_n as a function of transverse momentum and collision centrality, and study the correlations among the event planes of different order n. The v_n are well described by hydrodynamic models which employ a Glauber Monte Carlo initial state geometry with fluctuations, providing additional constraining power on the interplay between initial conditions and the effects of viscosity as the system evolves. This new constraint improves precision of the extracted viscosity to entropy density ratio eta/s.

The second Fourier component v_2 of the azimuthal anisotropy with respect to the reaction plane was measured for direct photons at midrapidity and transverse momentum (p_T) of 1--13 GeV/c in Au+Au collisions at sqr(s_NN)=200 GeV. Previous measurements of this quantity for hadrons with p_T < 6 GeV/c indicate that the medium behaves like a nearly perfect fluid, while for p_T > 6 GeV/c a reduced anisotropy is interpreted in terms of a path-length dependence for parton energy loss. In this measurement with the PHENIX detector at the Relativistic Heavy Ion Collider we find that for p_T > 4 GeV/c the anisotropy for direct photons is consistent with zero, as expected if the dominant source of direct photons is initial hard scattering. However, in the p_T < 4 GeV/c region dominated by thermal photons, we find a substantial direct photon v_2 comparable to that of hadrons, whereas model calculations for thermal photons in this kinematic region significantly underpredict the observed v_2.

The PHENIX experiment has measured midrapidity ([FORMULA: SEE TEXT]) transverse momentum spectra ([FORMULA: SEE TEXT]) of electrons as a function of centrality in Au+Au collisions at [FORMULA: SEE TEXT]. Contributions from photon conversions and from light hadron decays, mainly Dalitz decays of pi0 and eta mesons, were removed. The resulting nonphotonic electron spectra are primarily due to the semileptonic decays of hadrons carrying heavy quarks. Nuclear modification factors were determined by comparison to nonphotonic electrons in p+p collisions. A significant suppression of electrons at high pT is observed in central Au+Au collisions, indicating substantial energy loss of heavy quarks.

Azimuthal correlations of jet-induced high-p T charged hadron pairs are studied at midrapidity in Au Au collisions at s NN p 200 GeV.The distribution of jet-associated partner hadrons (1:0 < p T < 2:5 GeV=c) per trigger hadron (2:5 < p T < 4:0 GeV=c) is found to vary with collision centrality, in both shape and yield, indicating a significant effect of the nuclear collision medium on the jet fragmentation process.

The invariant differential cross section for inclusive neutral-pion production in p+p collisions at sqrt[s]=200 GeV has been measured at midrapidity (|eta|<0.35) over the range 1<p(T) less, similar 14 GeV/c by the PHENIX experiment at the Relativistic Heavy Ion Collider. Predictions of next-to-leading order perturbative QCD calculations are consistent with these measurements. The precision of our result is sufficient to differentiate between prevailing gluon-to-pion fragmentation functions.

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured charged hadron yields at midrapidity over a wide range of transverse momenta ͑0.5Ͻ p T Ͻ 10 GeV/ c͒ in Au+ Au collisions at ͱ s NN = 200 GeV.The data are compared to 0 measurements from the same experiment.For both charged hadrons and neutral pions, the yields per nucleon-nucleon collision are significantly suppressed in central compared to peripheral and nucleon-nucleon collisions.The suppression sets in gradually and increases with increasing centrality of the collisions.Above 4 -5 GeV/ c in p T , a constant and almost identical suppression of charged hadrons and 0 's is observed.The p T spectra are compared to published spectra from Au+ Au at ͱ s NN = 130 in terms of x T scaling.Central and peripheral 0 as well as peripheral charged spectra exhibit the same x T

The PHENIX experiment at the relativistic heavy ion collider (RHIC) has measured transverse energy and charged particle multiplicity at midrapidity in Au + Au collisions at center-of-mass energies130, and 200 GeV as a function of centrality.The presented results are compared to measurements from other RHIC experiments and experiments at lower energies.The √ s NN dependence of dE T /dη and dN ch /dη per pair of participants is consistent with logarithmic scaling for the most central events.The centrality dependence of dE T /dη and

We report on the yield of protons and antiprotons, as a function of centrality and transverse momentum, in Au+Au collisions at sqrt[s(NN)]=200 GeV measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider. In central collisions at intermediate transverse momenta (1.5<p(T)<4.5 GeV/c) a significant fraction of all produced particles are protons and antiprotons. They show a centrality-scaling behavior different from that of pions. The pmacr;/pi and p/pi ratios are enhanced compared to peripheral Au+Au, p+p, and e(+)e(-) collisions. This enhancement is limited to p(T)<5 GeV/c as deduced from the ratio of charged hadrons to pi(0) measured in the range 1.5<p(T)<9 GeV/c.

Inclusive transverse momentum spectra of eta mesons have been measured within p(T) = 2-10 GeV/c at midrapidity by the PHENIX experiment in Au + Au collisions at square root S(NN) = 200 GeV. In central Au+Au the eta yields are significantly suppressed compared to peripheral Au + Au, d + Au, and p + p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality, and p(T) dependence of the suppression is common, within errors, for eta and pi0. The ratio of eta to pi0 spectra at high p(T) amounts to 0.40 < R(eta/pi)0 < 0.48 for the three systems, in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e+e- collisions.

Heavy quarkonia are observed to be suppressed in relativistic heavy ion collisions relative to their production in p+p collisions scaled by the number of binary collisions. In order to determine if this suppression is related to color screening of these states in the produced medium, one needs to account for other nuclear modifications including those in cold nuclear matter. In this paper, we present new measurements from the PHENIX 2007 data set of J/psi yields at forward rapidity (1.2<|y|<2.2) in Au+Au collisions at sqrt(s_NN)=200 GeV. The data confirm the earlier finding that the suppression of J/psi at forward rapidity is stronger than at midrapidity, while also extending the measurement to finer bins in collision centrality and higher transverse momentum (pT). We compare the experimental data to the most recent theoretical calculations that incorporate a variety of physics mechanisms including gluon saturation, gluon shadowing, initial-state parton energy loss, cold nuclear matter breakup, color screening, and charm recombination. We find J/psi suppression beyond cold-nuclear-matter effects. However, the current level of disagreement between models and d+Au data precludes using these models to quantify the hot-nuclear-matter suppression.

Bose-Einstein correlations of identically charged pion pairs were measured by the PHENIX experiment at midrapidity in Au Au collisions at s NN p 200 GeV.The Bertsch-Pratt radius parameters were determined as a function of the transverse momentum of the pair and as a function of the centrality of the collision.Using the standard core-halo partial Coulomb fits, and a new parametrization which constrains the Coulomb fraction as determined from the unlike-sign pion correlation, the ratio R out =R side is within 0.8-1.1 for 0:25 < hk T i < 1:2 GeV=c.The centrality dependence of all radii is well described by a linear scaling in N 1=3 part

The dependence of transverse momentum spectra of neutral pions and $\ensuremath{\eta}$ mesons with ${p}_{T}&lt;16\text{ }\text{ }\mathrm{GeV}/c$ and ${p}_{T}&lt;12\text{ }\text{ }\mathrm{GeV}/c$, respectively, on the centrality of the collision has been measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) in $d+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$. The measured yields are compared to those in $p+p$ collisions at the same $\sqrt{{s}_{NN}}$ scaled by the number of underlying nucleon-nucleon collisions in $d+\mathrm{Au}$. At all centralities, the yield ratios show no suppression, in contrast to the strong suppression seen for central $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC. Only a weak ${p}_{T}$ and centrality dependence can be observed.

Transverse single-spin asymmetries to probe the transverse-spin structure of the proton have been measured for neutral pions and nonidentified charged hadrons from polarized proton-proton collisions at midrapidity and s p 200 GeV.The data cover a transverse momentum (p T ) range 1:0-5:0 GeV=c for neutral pions and 0:5-5:0 GeV=c for charged hadrons, at a Feynman-x value of approximately zero.The asymmetries seen in this previously unexplored kinematic region are consistent

Cross sections for midrapidity production of direct photons in p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are reported for transverse momenta of 3 < pT < 16 GeV/c. Next-to-leading order perturbative QCD (pQCD) describes the data well for pT >5 GeV/c, where the uncertainties of the measurement and theory are comparable. We also report on the effect of requiring the photons to be isolated from parton jet energy. The observed fraction of isolated photons is well described by pQCD for pT >7 GeV/c.

The PHENIX experiment has measured the production of neutral pions in Au+Au collisions at sqrt(s_NN)=200 GeV. The new data offer a fourfold increase in recorded luminosity, providing higher precision and a larger reach in transverse momentum, p_T, to 20 GeV/c. The production ratio of eta/pi^0 is 0.46+/-0.01(stat)+/-0.05(syst), constant with p_T and collision centrality. The observed ratio is consistent with earlier measurements, as well as with the p+p and d+Au values. The production of pi^0 is suppressed by a factor of 5, as in earlier findings. However, with the improved statistical precision a small but significant rise of the nuclear modification factor, R_AA, vs p_T, with a slope of 0.0106+/-^(0.0034)_(0.0029)[GeV/c]^-1, is discernible in central collisions. A phenomenological extraction of the average fractional parton energy loss shows a decrease with increasing p_T. To study the path length dependence of suppression, the pi^0 yield was measured at different angles with respect to the event plane; a strong azimuthal dependence of the pi^0 R_AA is observed. The data are compared to theoretical models of parton energy loss as a function of the path length, L, in the medium. Models based on pQCD are insufficient to describe the data, while a hybrid model utilizing pQCD for the hard interactions and AdS/CFT for the soft interactions is consistent with the data.

Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-Dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop Tomography of the Quark-Gluon Plasma with Heavy Quarks, which was held in October 2016 in Leiden, The Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma.

We present a new measurement of the spin-dependent structure function g1d of the deuteron in deep inelastic scattering of 190 GeV polarised muons on polarised deuterons, in the kinematic range 0.003 < x < 0.7 and 1 GeV2 < Q2 < 60 GeV2. This structure function is found to be negative at small x. The first moment Γ1d=∫01g1ddx evaluated at Q02 = 10 GeV2 is 0.034 ± 0.009 (stat.) ± 0.006 (syst.). This value is below the Ellis-Jaffe sum rule prediction by three standard deviations. Using our earlier determination of Γ1p, we obtain Γ1p − Γ1n = 0.199 ± 0.038 which agrees with the Bjorken sum rule.

The PHENIX experiment has measured midrapidity transverse momentum spectra (0.4<p(T)<4.0 GeV/c) of single electrons as a function of centrality in Au+Au collisions at sqrt[s(NN)]=200 GeV. Contributions from photon conversions and Dalitz decays of light neutral mesons are measured by introducing a thin (1.7% X0) converter into the PHENIX acceptance and are statistically removed. The subtracted nonphotonic electron spectra are primarily due to the semileptonic decays of hadrons containing heavy quarks, mainly charm at lower p(T). For all centralities, the charm production cross section is found to scale with the nuclear overlap function, T(AA). For minimum-bias collisions the charm cross section per binary collision is N(cc )/T(AA)=622+/-57(stat)+/-160(syst) microb.

J/psi production in d + Au and p + p collisions at square root of S(NN) = 200 GeV has been measured by the PHENIX experiment at rapidities -2.2 < y < +2.4. The cross sections and nuclear dependence of J/psi production versus rapidity, transverse momentum, and centrality are obtained and compared to lower energy p + A results and to theoretical models. The observed nuclear dependence in d + Au collisions is found to be modest, suggesting that the absorption in the final state is weak and the shadowing of the gluon distributions is small and consistent with Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-based parametrizations that fit deep-inelastic scattering and Drell-Yan data at lower energies.

Differential elliptic flow (v2) for ϕ mesons and (anti)deuterons (¯d)d is measured for Au+Au collisions at √sNN=200 GeV. The v2 for ϕ mesons follows the trend of lighter π± and K± mesons, suggesting that ordinary hadrons interacting with standard hadronic cross sections are not the primary driver for elliptic flow development. The v2 values for (¯d)d suggest that elliptic flow is additive for composite particles. This further validation of the universal scaling of v2 per constituent quark for baryons and mesons suggests that partonic collectivity dominates the transverse expansion dynamics.Received 14 March 2007DOI:https://doi.org/10.1103/PhysRevLett.99.052301©2007 American Physical Society

We present the first measurement of photoproduction of J/psi and of two-photon production of high-mass e+e- pairs in electromagnetic (or ultra-peripheral) nucleus-nucleus interactions, using Au+Au data at sqrt(s_NN) = 200 GeV. The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au^{star} nuclei. The event sample consists of 28 events with m_{e+e-} > 2 GeV/c^2 with zero like-sign background. The measured cross sections at midrapidity of d\sigma / dy (J/psi + Xn, y=0) = 76 +/- 33 (stat) +/- 11 (syst) micro b and d^2\sigma/dm dy (e^+e^- + Xn, y=0) = 86 +/- 23 (stat) +/- 16 (syst) micro b/(GeV/c^2) for m_{e+e-} \in [2.0,2.8] GeV/c^2 are consistent with various theoretical predictions.

We have measured the azimuthal anisotropy of π⁰ production for 1<p(T)<18 GeV/c for Au+Au collisions at sqrt((s)NN)=200 GeV. The observed anisotropy shows a gradual decrease for 3≲p(T)≲7-10 GeV/c, but remains positive beyond 10 GeV/c. The magnitude of this anisotropy is underpredicted, up to at least ∼10 GeV/c, by current perturbative QCD (PQCD) energy-loss model calculations. An estimate of the increase in anisotropy expected from initial-geometry modification due to gluon saturation effects and fluctuations is insufficient to account for this discrepancy. Calculations that implement a path-length dependence steeper than what is implied by current PQCD energy-loss models show reasonable agreement with the data.

Measurements of neutral pion (π0) production at midrapidity in √sNN=200 GeV Au+Au collisions as a function of transverse momentum, pT, collision centrality, and angle with respect to reaction plane are presented. The data represent the final π0 results from the PHENIX experiment for the first RHIC Au+Au run at design center-of-mass energy. They include additional data obtained using the PHENIX Level-2 trigger with more than a factor of 3 increase in statistics over previously published results for pT>6 GeV/c. We evaluate the suppression in the yield of high-pT π0's relative to pointlike scaling expectations using the nuclear modification factor RAA. We present the pT dependence of RAA for nine bins in collision centrality. We separately integrate RAA over larger pT bins to show more precisely the centrality dependence of the high-pT suppression. We then evaluate the dependence of the high-pT suppression on the emission angle Δϕ of the pions with respect to event reaction plane for seven bins in collision centrality. We show that the yields of high-pT π0's vary strongly with Δϕ, consistent with prior measurements [1,2]. We show that this variation persists in the most peripheral bin accessible in this analysis. For the peripheral bins we observe no suppression for neutral pions produced aligned with the reaction plane, whereas the yield of π0's produced perpendicular to the reaction plane is suppressed by a factor of ~2. We analyze the combined centrality and Δϕ dependence of the π0 suppression in different pT bins using different possible descriptions of parton energy loss dependence on jet path-length averages to determine whether a single geometric picture can explain the observed suppression pattern.14 MoreReceived 7 November 2006DOI:https://doi.org/10.1103/PhysRevC.76.034904©2007 American Physical Society

Differential measurements of the elliptic (v(2)) and hexadecapole (v(4)) Fourier flow coefficients are reported for charged hadrons as a function of transverse momentum (p(T)) and collision centrality or number of participant nucleons (N(part)) for Au+Au collisions at sq.rt(s(NN))=200 GeV. The v(2,4) measurements at pseudorapidity |η|≤0.35, obtained with four separate reaction-plane detectors positioned in the range 1.0<|η|<3.9, show good agreement, indicating the absence of significant Δη-dependent nonflow correlations. Sizable values for v(4)(p(T)) are observed with a ratio v(4)(p(T),N(part))/v(2)(2)(p(T),N(part))≈0.8 for 50≲N(part)≲200, which is compatible with the combined effects of a finite viscosity and initial eccentricity fluctuations. For N(part)≳200 this ratio increases up to 1.7 in the most central collisions.

We report the measurement of direct photons at midrapidity in Au+Au collisions at sqrt{s_NN} = 200 GeV. The direct photon signal was extracted for the transverse-momentum range of 4 GeV/c < p_T < 22 GeV/c, using a statistical method to subtract decay photons from the inclusive-photon sample. The direct-photon nuclear-modification factor R_AA was calculated as a function of p_T for different Au+Au collision centralities using the measured p+p direct-photon spectrum and compared to theoretical predictions. R_AA was found to be consistent with unity for all centralities over the entire measured p_T range. Theoretical models that account for modifications of initial-direct-photon production due to modified-parton-distribution functions in Au and the different isospin composition of the nuclei, predict a modest change of R_AA from unity and are consistent with the data. Models with compensating effects of the quark-gluon plasma on high-energy photons, such as suppression of jet-fragmentation photons and induced-photon bremsstrahlung from partons traversing the medium, are also consistent with this measurement.

We present inclusive charged hadron elliptic flow v_2 measured over the pseudorapidity range |\eta| < 0.35 in Au+Au collisions at sqrt(s_NN) = 200 GeV. Results for v_2 are presented over a broad range of transverse momentum (p_T = 0.2-8.0 GeV/c) and centrality (0-60%). In order to study non-flow effects that are not correlated with the reaction plane, as well as the fluctuations of v_2, we compare two different analysis methods: (1) event plane method from two independent sub-detectors at forward (|\eta| = 3.1-3.9) and beam (|\eta| > 6.5) pseudorapidities and (2) two-particle cumulant method extracted using correlations between particles detected at midrapidity. The two event-plane results are consistent within systematic uncertainties over the measured p_T and in centrality 0-40%. There is at most 20% difference of the v_2 between the two event plane methods in peripheral (40-60%) collisions. The comparisons between the two-particle cumulant results and the standard event plane measurements are discussed.

Measurements of the anisotropy parameter ${v}_{2}$ of identified hadrons (pions, kaons, and protons) as a function of centrality, transverse momentum ${p}_{T}$, and transverse kinetic energy KE${}_{T}$ at midrapidity ($|\ensuremath{\eta}|&lt;0.35$) in Au + Au collisions at $\sqrt{{s}_{NN}}=200$ GeV are presented. Pions and protons are identified up to ${p}_{T}=$ 6 GeV$/c$, and kaons up to ${p}_{T}=$ 4 GeV$/c$, by combining information from time-of-flight and aerogel \ifmmode \check{C}\else \v{C}\fi{}erenkov detectors in the PHENIX Experiment. The scaling of ${v}_{2}$ with the number of valence quarks (${n}_{q}$) has been studied in different centrality bins as a function of transverse momentum and transverse kinetic energy. A deviation from previously observed quark-number scaling is observed at large values of KE${}_{T}/{n}_{q}$ in noncentral Au + Au collisions ($20--60%$), but this scaling remains valid in central collisions ($0--10%$).

Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, $A_{LL}$, for $\pi^0$ and $\eta$ production in $\sqrt{s} = 200$ GeV polarized $p$$+$$p$ collisions. Comparison of the $\pi^0$ results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, $\Delta G$, in the proton in the probed Bjorken $x$ range. The effect of adding the new 2009 \pz data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}} = 0.06^{+0.11}_{-0.15}$ in the range $0.05<x<0.2$, with the uncertainty at $\Delta \chi^2 = 9$ when considering only statistical experimental uncertainties. Shifting the PHENIX data points by their systematic uncertainty leads to a variation of the best-fit value of $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}}$ between $0.02$ and $0.12$, demonstrating the need for full treatment of the experimental systematic uncertainties in future global analyses.

PHENIX has measured the centrality dependence of midrapidity pion, kaon, and proton transverse momentum distributions in d + Au and p + p collisions at √ s NN = 200 GeV.The p + p data provide a reference for nuclear effects in d + Au and previously measured Au + Au collisions.Hadron production is enhanced in d + Au, relative to independent nucleon-nucleon scattering, as was observed in lower

We present the results of φ meson production in the K + K -decay channel from Au+Au collisions at √ s NN = 200 GeV as measured at midrapidity by the PHENIX detector at Brookhaven National Laboratory's Relativistic Heavy Ion Collider.Precision resonance centroid and width values are extracted as a function of collision centrality.No significant variation from the Particle Data Group accepted values is observed, contrary to some model predictions.The φ transverse mass spectra are fitted with a linear exponential function for which the derived inverse slope parameter is seen to be constant as a function of centrality.However, when these data are fitted by a hydrodynamic model the result is that the centrality-dependent freeze-out temperature and the expansion velocity values

width of the away-side peak is shown to be a convolution of j T with the fragmentation variable, z, and the partonic transverse momentum, k T .The hzi is determined through a combined analysis of the measured 0 inclusive and associated spectra using jet-fragmentation functions measured in e e ÿ collisions.The final extracted values of k T are then determined to also be independent of the trigger particle transverse momentum, over the

Large parity-violating longitudinal single-spin asymmetries A(L)(e+) = -0.86(-0.14) (+0.30) and A(L)(e-) = 0.88(-0.71) (+0.12) are observed for inclusive high transverse momentum electrons and positrons in polarized p+p collisions at a center-of-mass energy of sqrt[s] = 500 GeV with the PHENIX detector at RHIC. These e± come mainly from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W± boson production cross sections for the e± channels of σ(pp → W+ X) × BR(W+ → e+ ν(e)) = 144.1 ± 21.2(stat)(-10.3) (+3.4) (syst) ± 21.6(norm) pb, and σ(pp → W- X) × BR(W- → e- ν[over ¯](e)) = 31.7 ± 12.1(stat)(-8.2) (+10.1) (syst) ± 4.8(norm) pb.

Event-by-event fluctuations of the average transverse momentum of produced particles near midrapidity have been measured by the PHENIX Collaboration in $\sqrt{{s}_{NN}}=200\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$ $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$, and $p+p$ collisions at the Relativistic Heavy Ion Collider. The fluctuations are observed to be in excess of the expectation for statistically independent particle emission for all centralities. The excess fluctuations exhibit a dependence on both the centrality of the collision and on the ${p}_{T}$ range over which the average is calculated. Both the centrality and ${p}_{T}$ dependence can be well reproduced by a simulation of random particle production with the addition of contributions from hard-scattering processes.

We report on charged hadron production in deuteron-gold reactions at sqrt[s(NN)]=200 GeV. Our measurements in the deuteron direction cover 1.4<eta<2.2, referred to as forward rapidity, and in the gold direction -2.0<eta<-1.4, referred to as backward rapidity, and a transverse momentum range p(T)=0.5-4.0 GeV/c. We compare the relative yields for different deuteron-gold collision centrality classes. We observe a suppression relative to binary collision scaling at forward rapidity, sensitive to low momentum fraction (x) partons in the gold nucleus, and an enhancement at backward rapidity, sensitive to high momentum fraction partons in the gold nucleus.

The production of deuterons and antideuterons in the transverse momentum range 1.1<p(T)<4.3 GeV/c at midrapidity in Au+Au collisions at square root of s(NN)=200 GeV has been studied by the PHENIX experiment at RHIC. A coalescence analysis, comparing the deuteron and antideuteron spectra with that of proton and antiproton, has been performed. The coalescence probability is equal for both deuterons and antideuterons and it increases as a function of p(T), which is consistent with an expanding collision zone. Comparing (anti)proton yields, p /p=0.73+/-0.01, with (anti)deuteron yields, d /d=0.47+/-0.03, we estimate that n /n=0.64+/-0.04. The nucleon phase space density is estimated from the coalescence measurement.

The transverse momentum dependence of the azimuthal anisotropy parameter v 2 , the second harmonic of the azimuthal distribution, for electrons at midrapidity (|η| < 0.35) has been measured with the PHENIX detector in Au+Au collisions at √ s NN = 200 GeV.The measurement was made with respect to the reaction plane defined at high rapidities (|η| = 3.1-3.9).From the result we have measured the v 2 of electrons from heavy flavor decay after subtraction of the v 2 of electrons from other sources such as photon conversions and Dalitz decay from light neutral mesons.We observe a nonzero single electron v 2 with a 90% confidence level in the

Measurements of the azimuthal anisotropy of high-${p}_{T}$ neutral pion (${\ensuremath{\pi}}^{0}$) production in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{{}_{\mathit{NN}}}}=200$ GeV by the PHENIX experiment are presented. The data included in this article were collected during the 2004 Relativistic Heavy Ion Collider running period and represent approximately an order of magnitude increase in the number of analyzed events relative to previously published results. Azimuthal angle distributions of ${\ensuremath{\pi}}^{0}$ mesons detected in the PHENIX electromagnetic calorimeters are measured relative to the reaction plane determined event-by-event using the forward and backward beam-beam counters. Amplitudes of the second Fourier component (${v}_{2}$) of the angular distributions are presented as a function of ${\ensuremath{\pi}}^{0}$ transverse momentum (${p}_{T}$) for different bins in collision centrality. Measured reaction plane dependent ${\ensuremath{\pi}}^{0}$ yields are used to determine the azimuthal dependence of the ${\ensuremath{\pi}}^{0}$ suppression as a function of ${p}_{T}$, ${R}_{\mathrm{AA}}(\ensuremath{\Delta}\ensuremath{\phi},{p}_{T})$. A jet-quenching motivated geometric analysis is presented that attempts to simultaneously describe the centrality dependence and reaction plane angle dependence of the ${\ensuremath{\pi}}^{0}$ suppression in terms of the path lengths of hypothetical parent partons in the medium. This set of results allows for a detailed examination of the influence of geometry in the collision region and of the interplay between collective flow and jet-quenching effects along the azimuthal axis.

The result of a search at the LHC for heavy stable charged particles produced in pp collisions at $ \sqrt {s} = 7\;{\text{TeV}} $ is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb−1. Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398GeV/c 2, using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c 2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.

Hadronic event shapes have been measured in proton-proton collisions at sqrt(s)=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.

A measurement of the top-antitop production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the top-antitop signal from W+jets and QCD multijet background events. The measured cross section is 173 + 39 - 32 (stat. + syst.) pb, consistent with standard model expectations.

Neutral-pion π(0) spectra were measured at midrapidity (|y|<0.35) in Au+Au collisions at √(s(NN))=39 and 62.4 GeV and compared with earlier measurements at 200 GeV in a transverse-momentum range of 1<p(T)<10 GeV/c. The high-p(T) tail is well described by a power law in all cases, and the powers decrease significantly with decreasing center-of-mass energy. The change of powers is very similar to that observed in the corresponding spectra for p+p collisions. The nuclear modification factors (R(AA)) show significant suppression, with a distinct energy, centrality, and p(T) dependence. Above p(T)=7 GeV/c, R(AA) is similar for √(s(NN))=62.4 and 200 GeV at all centralities. Perturbative-quantum-chromodynamics calculations that describe R(AA) well at 200 GeV fail to describe the 39 GeV data, raising the possibility that, for the same p(T) region, the relative importance of initial-state effects and soft processes increases at lower energies. The p(T) range where π(0) spectra in central Au+Au collisions have the same power as in p+p collisions is ≈5 and 7 GeV/c for √(s(NN))=200 and 62.4 GeV, respectively. For the √(s(NN))=39 GeV data, it is not clear whether such a region is reached, and the x(T) dependence of the x(T)-scaling power-law exponent is very different from that observed in the √(s(NN))=62 and 200 GeV data, providing further evidence that initial-state effects and soft processes mask the in-medium suppression of hard-scattered partons to higher p(T) as the collision energy decreases.

New PHENIX measurements of the anisotropic flow coefficients $v_2\{\Psi_2\}$, $v_3\{\Psi_3\}$, $v_4\{\Psi_4\}$ and $v_4\{\Psi_2\}$ for identified particles ($\pi^{\pm}$, $K^{\pm}$, and $p+\bar{p}$) obtained relative to the event planes $\Psi_n$ in Au$+$Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV are presented as functions of collision centrality and particle transverse momenta $p_T$. The $v_n$ coefficients show characteristic patterns consistent with hydrodynamical expansion of the matter produced in the collisions. For each harmonic $n$, a modified valence quark number $n_q$ scaling plotting $v_n/(n_q)^{n/2}$ versus ${\rm KE}_T/n_q$ is observed to yield a single curve for all the measured particle species for a broad range of transverse kinetic energies ${\rm KE}_T$. A simultaneous blast wave model fit to the observed particle spectra and $v_n(p_T)$ coefficients identifies spatial eccentricities $s_n$ at freeze-out, which are much smaller than the initial-state geometric values.

The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 inverse femtobarns, were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A[c,y] = [0.33 +/- 0.26 (stat) +/- 0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

First results on charm quarkonia production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are presented.The yield of J/'s measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au-Au reactions at ͱ s NN = 200 GeV is analyzed as a function of collision centrality.For this analysis we have studied 49.3ϫ 10 6 minimum bias Au-Au reactions.We present the J/ invariant yield dN/dy for peripheral and midcentral reactions.For the most central collisions where we observe no signal above background, we quote 90% confidence level upper limits.We compare these results with our J/ measurement from proton-proton reactions at the same energy.We find that our measurements are not consistent with models that predict strong enhancement relative to binary collision scaling.

J/psi production has been measured in proton-proton collisions at square root of s=200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at the Relativistic Heavy Ion Collider. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 4.0+/-0.6(stat)+/-0.6(syst)+/-0.4(abs) mu b. The mean transverse momentum is 1.80+/-0.23(stat)+/-0.16(syst) GeV/c.

We present a measurement of the double longitudinal spin asymmetry in inclusive ${\ensuremath{\pi}}^{0}$ production in polarized proton-proton collisions at $\sqrt{s}=200\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$. The data were taken at the Relativistic Heavy Ion Collider with average beam polarizations of 0.27. The measurements are the first in a program to study the longitudinal spin structure of the proton, using strongly interacting probes, at collider energies. The asymmetry is presented for transverse momenta $1--5\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/c$ at midrapidity, where next-to-leading-order perturbative quantum chromodynamic (NLO pQCD) calculations well describe the unpolarized cross section. The observed asymmetry is small and is compared to a NLO pQCD calculation with a range of polarized gluon distributions.

Dihadron correlations at high transverse momentum in d+Au collisions at sqrt(s_NN) = 200 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). From these correlations we extract several structural characteristics of jets; the root-mean-squared (RMS) transverse momentum of fragmenting hadrons with respect to the jet sqrt(<j_T^2>), the mean sine-squared angle between the scattered partons <sin^2(phi_jj)>, and the number of particles produced within the dijet that are associated with a high-p_T particle (dN/dx_E distributions). We observe that the fragmentation characteristics of jets in d+Au collisions are very similar to those in p+p collisions and that there is also little dependence on the centrality of the d+Au collision. This is consistent with the nuclear medium having little influence on the fragmentation process. Furthermore, there is no statistically significant increase in the value of <sin^2(phi_jj)> from p+p to d+Au collisions. This constrains the amount of multiple scattering that partons undergo in the cold nuclear medium before and after a hard-collision.

The azimuthal distribution of identified pi0 and inclusive photons has been measured in [FORMULA: SEE TEXT] Au+Au collisions with the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The second-harmonic parameter (nu2) was measured to describe the observed anisotropy of the azimuthal distribution. The measured inclusive photon is consistent with the value expected for the photons from hadron decay and is also consistent with the lack of direct photon signal over the measured pT range 1-6 GeV/c. An attempt is made to extract nu2 of direct photons.

The PHENIX Muon Arms detect muons at rapidities of |y|=(1.2–2.4) with full azimuthal acceptance. Each muon arm must track and identify muons and provide good rejection of pions and kaons (∼10−3). In order to accomplish this we employ a radial field magnetic spectrometer with precision tracking (Muon Tracker) followed by a stack of absorber/low resolution tracking layers (Muon Identifier). The design, construction, testing and expected run parameters of both the muon tracker and the muon identifier are described.

The invariant differential cross section for inclusive electron production in $p+p$ collisions at $\sqrt{s}=200\text{ }\text{ }\mathrm{GeV}$ has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over the transverse momentum range $0.4\ensuremath{\le}{p}_{T}\ensuremath{\le}5.0\text{ }\text{ }\mathrm{GeV}/c$ in the central rapidity region ($|\ensuremath{\eta}|\ensuremath{\le}0.35$). The contribution to the inclusive electron spectrum from semileptonic decays of hadrons carrying heavy flavor, i.e., charm quarks or, at high ${p}_{T}$, bottom quarks, is determined via three independent methods. The resulting electron spectrum from heavy-flavor decays is compared to recent leading and next-to-leading order perturbative QCD calculations. The total cross section of charm quark-antiquark pair production is determined to be ${\ensuremath{\sigma}}_{c\overline{c}}=0.92\ifmmode\pm\else\textpm\fi{}0.15(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.54(\mathrm{syst})\text{ }\text{ }\mathrm{mb}$.

Emission source functions are extracted from correlation functions constructed from charged pions produced at midrapidity in Au Au collisions at s NN p 200 GeV.The source parameters extracted from these functions at low k T give first indications of a long tail for the pion emission source.The

A three-dimensional correlation function obtained from midrapidity, low pT, pion pairs in central Au+Au collisions at √sNN=200 GeV is studied. The extracted model-independent source function indicates a long range tail in the directions of the pion pair transverse momentum (out) and the beam (long). A proper breakup time τ0∼9 fm/c and a mean proper emission duration Δτ∼2 fm/c, leading to sizable emission time differences (⟨|ΔtLCM|⟩≈12 fm/c), are required to allow models to be successfully matched to these tails. The model comparisons also suggest an outside-in "burning" of the emission source reminiscent of many hydrodynamical models.Received 28 December 2007DOI:https://doi.org/10.1103/PhysRevLett.100.232301©2008 American Physical Society

Bose-Einstein correlations of charged kaons are used to

A measurement of direct photons in $p+p$ collisions at $\sqrt{s}=200\text{ }\text{ }\mathrm{GeV}$ is presented. A photon excess above background from ${\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}\ensuremath{\gamma}+\ensuremath{\gamma}$, $\ensuremath{\eta}\ensuremath{\rightarrow}\ensuremath{\gamma}+\ensuremath{\gamma}$ and other decays is observed in the transverse momentum range $5.5&lt;{p}_{\mathrm{T}}&lt;7\text{ }\text{ }\mathrm{GeV}/c$. The result is compared to a next-to-leading-order perturbative QCD calculation. Within errors, good agreement is found between the QCD calculation and the measured result.

Muon production at forward rapidity (1.5≤|η|≤1.8) has been measured by the PHENIX experiment over the transverse momentum range 1≤pT≤3 GeV/c in √s=200 GeV p+p collisions at the Relativistic Heavy Ion Collider. After statistically subtracting contributions from light hadron decays an excess remains which is attributed to the semileptonic decays of hadrons carrying heavy flavor, i.e. charm quarks or, at high pT, bottom quarks. The resulting muon spectrum from heavy flavor decays is compared to PYTHIA and a next-to-leading-order perturbative QCD calculation. PYTHIA is used to determine the charm quark spectrum that would produce the observed muon excess. The corresponding differential cross section for charm quark production at forward rapidity is determined to be dσc¯c/dy|y=1.6=0.243±0.013(stat.)±0.105(data syst.)+0.049−0.087(PYTHIA syst.) mb.11 MoreReceived 18 September 2006DOI:https://doi.org/10.1103/PhysRevD.76.092002©2007 American Physical Society

Charged-pion-interferometry measurements were made with respect to the second- and third-order event plane for $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\mathrm{GeV}$. A strong azimuthal-angle dependence of the extracted Gaussian-source radii was observed with respect to both the second- and third-order event planes. The results for the second-order dependence indicate that the initial eccentricity is reduced during the medium evolution, which is consistent with previous results. In contrast, the results for the third-order dependence indicate that the initial triangular shape is significantly reduced and potentially reversed by the end of the medium evolution, and that the third-order oscillations are largely dominated by the dynamical effects from triangular flow.

We present measurements of the J/psi invariant yields in sqrt(s_NN)=39 and 62.4 GeV Au+Au collisions at forward rapidity (1.2

Longitudinal density correlations of produced matter in Au+Au collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV have been measured from the inclusive charged particle distributions as a function of pseudorapidity window sizes. The extracted $\ensuremath{\alpha}\ensuremath{\xi}$ parameter, related to the susceptibility of the density fluctuations in the long-wavelength limit, exhibits a nonmonotonic behavior as a function of the number of participant nucleons, ${N}_{\mathrm{part}}$. A local maximum is seen at ${N}_{\mathrm{part}}~90$, with corresponding energy density based on the Bjorken picture of ${\ensuremath{\epsilon}}_{\mathrm{Bj}}\ensuremath{\tau}~2.4$ GeV/(fm${}^{2}c)$ with a transverse area size of 60 fm${}^{2}$. This behavior may suggest a critical phase boundary based on the Ginzburg-Landau framework.

The PHENIX experiment at RHIC has measured the invariant cross section for \ensuremath{\omega}-meson production at midrapidity in the transverse momentum range $2.5&lt;{p}_{T}&lt;9.25$ GeV/$c$ in $p+p$ and $d$+Au collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV. Measurements in two decay channels ($\ensuremath{\omega}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and $\ensuremath{\omega}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$) yield consistent results, and the reconstructed \ensuremath{\omega} mass agrees with the accepted value within the ${p}_{T}$ range of the measurements. The $\ensuremath{\omega}/{\ensuremath{\pi}}^{0}$ ratio is found to be $0.85\ifmmode\pm\else\textpm\fi{}0.{05}^{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{09}^{\mathrm{sys}}$ in $p+p$ and $0.94\ifmmode\pm\else\textpm\fi{}0.{08}^{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{12}^{\mathrm{sys}}$ in $d$+Au collisions, independent of ${p}_{T}$. The nuclear modification factor ${R}_{d\mathrm{A}}^{\ensuremath{\omega}}$ is $1.03\ifmmode\pm\else\textpm\fi{}0.{12}^{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{21}^{\mathrm{sys}}$ and $0.83\ifmmode\pm\else\textpm\fi{}0.{21}^{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{17}^{\mathrm{sys}}$ in minimum bias and central (0--20%) $d$+Au collisions, respectively.

We present measurements of electrons and positrons from the semileptonic decays of heavy-flavor hadrons at midrapidity ($|y|&lt;$ 0.35) in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=62.4$ GeV. The data were collected in 2010 by the PHENIX experiment that included the new hadron-blind detector. The invariant yield of electrons from heavy-flavor decays is measured as a function of transverse momentum in the range $1&lt;{p}_{T}^{e}&lt;5$ GeV/$c$. The invariant yield per binary collision is slightly enhanced above the $p+p$ reference in $\mathrm{Au}+\mathrm{Au}$ 0%--20%, 20%--40%, and 40%--60% centralities at a comparable level. At this low beam energy this may be a result of the interplay between initial-state Cronin effects, final-state flow, and energy loss in medium. The ${v}_{2}$ of electrons from heavy-flavor decays is nonzero when averaged between $1.3&lt;{p}_{T}^{e}&lt;2.5$ GeV/$c$ for 0%--40% centrality collisions at $\sqrt{{s}_{NN}}=62.4$ GeV. For 20%--40% centrality collisions, the ${v}_{2}$ at $\sqrt{{s}_{NN}}=62.4$ GeV is smaller than that for heavy-flavor decays at $\sqrt{{s}_{NN}}=200$ GeV. The ${v}_{2}$ of the electrons from heavy-flavor decay at the lower beam energy is also smaller than ${v}_{2}$ for pions. Both results indicate that the heavy quarks interact with the medium formed in these collisions, but they may not be at the same level of thermalization with the medium as observed at $\sqrt{{s}_{NN}}=200$ GeV.

Deuteron-gold (d Au) collisions at the Relativistic Heavy Ion Collider provide ideal platforms for testing QCD theories in dense nuclear matter at high energy.In particular, models suggesting strong saturation effects for partons carrying small nucleon momentum fraction (x) predict modifications to jet production

We present transverse momentum (p_T) spectra of charged hadrons measured in deuteron-gold and nucleon-gold collisions at \sqrts = 200 GeV for four centrality classes. Nucleon-gold collisions were selected by tagging events in which a spectator nucleon was observed in one of two forward rapidity detectors. The spectra and yields were investigated as a function of the number of binary nucleon-nucleon collisions, ν, suffered by deuteron nucleons. A comparison of charged particle yields to those in p+p collisions show that the yield per nucleon-nucleon collision saturates with νfor high momentum particles. We also present the charged hadron to neutral pion ratios as a function of p_T.

The azimuthal anisotropy coefficients ${v}_{2}$ and ${v}_{4}$ of ${\ensuremath{\pi}}^{0}$ and $\ensuremath{\eta}$ mesons are measured in Au + Au collisions at $\sqrt{{s}_{\mathit{\text{NN}}}}=200$ GeV as a function of transverse momentum ${p}_{T}$ (1--14 GeV/$c$) and centrality. The extracted ${v}_{2}$ coefficients are found to be consistent between the two meson species over the measured ${p}_{T}$ range. The ratio of ${v}_{4}/{v}_{2}^{2}$ for ${\ensuremath{\pi}}^{0}$ mesons is found to be independent of ${p}_{T}$ for 1--9 GeV/$c$, implying a lack of sensitivity of the ratio to the change of underlying physics with ${p}_{T}$. Furthermore, the ratio of ${v}_{4}/{v}_{2}^{2}$ is systematically larger in central collisions, which may reflect the combined effects of fluctuations in the initial collision geometry and finite viscosity in the evolving medium.

A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 137 fb$^{-1}$, recorded with the CMS detector. The coupling strength with respect to the standard model value, $Y_\mathrm{t}$, is determined from kinematic distributions in $\mathrm{t\bar{t}}$ final states containing ee, $μμ$, or e$μ$ pairs. Variations of the Yukawa coupling strength lead to modified distributions for $\mathrm{t\bar{t}}$ production. In particular, the distributions of the mass of the $\mathrm{t\bar{t}}$ system and the rapidity difference of the top quark and antiquark are sensitive to the value of $Y_\mathrm{t}$. The measurement yields a best fit value of $Y_\mathrm{t} =$ 1.16 $^{+0.24}_{-0.35}$, bounding $Y_\mathrm{t}$ $\lt$ 1.54 at a 95% confidence level.

PHENIX has measured J/ψ production at backward, central and forward rapidities both in p+p and d+Au collisions at during the third run of the RHIC collider. From the p+p collisions, we measure the total J/ψ cross section. From the d+Au collisions, we compute the nuclear modification factor versus transverse momentum, rapidity and centrality. All results presented here are preliminary.

I present here a new Glauber-inspired approach to derive normal cold nuclear matter effects on $J/ψ$ production in Au-Au collisions. In an as much as possible model-independent way, it extrapolates the centrality dependent yields from d-Au to Au-Au collisions. I then compare to the new Au-Au measurements shown by the PHENIX experiment in this conference. In the most central collisions, $J/ψ$ survival probabilities beyond cold nuclear matter effects are found to be $44\pm23%$ at forward ($y=1.7$) and $25\pm12%$ at mid ($y=0$) rapidities.

We address the question of understanding the production of J/ψ particles regarding the global underlying event in proton-proton collisions. To do so, we propose to look at a new observable: the J/ψ production as a function of the charged particles multiplicity of the event. We demonstrate the interest for an experimental measurement by varying the model of multiple interactions in the PYTHIA generator.

We present midrapidity charged-pion invariant cross sections, the ratio of the ${\ensuremath{\pi}}^{\ensuremath{-}}$ to ${\ensuremath{\pi}}^{+}$ cross sections and the charge-separated double-spin asymmetries in polarized $p+p$ collisions at $\sqrt{s}=200\text{ }\mathrm{GeV}$. While the cross section measurements are consistent within the errors of next-to-leading-order (NLO) perturbative quantum chromodynamics predictions (pQCD), the same calculations overestimate the ratio of the charged-pion cross sections. This discrepancy arises from the cancellation of the substantial systematic errors associated with the NLO-pQCD predictions in the ratio and highlights the constraints these data will place on flavor-dependent pion fragmentation functions. The charge-separated pion asymmetries presented here sample an $x$ range of $\ensuremath{\sim}0.03--0.16$ and provide unique information on the sign of the gluon-helicity distribution.

We report on the first measurement of the double-spin asymmetry, ${A}_{LL}$, of electrons from the decays of hadrons containing heavy flavor in longitudinally polarized $p+p$ collisions at $\sqrt{s}=200\text{ }\text{ }\mathrm{GeV}$ for ${p}_{T}=0.5$ to $3.0\text{ }\text{ }\mathrm{GeV}/c$. The asymmetry was measured at midrapidity ($|\ensuremath{\eta}|&lt;0.35$) with the PHENIX detector at the Relativistic Heavy Ion Collider. The measured asymmetries are consistent with zero within the statistical errors. We obtained a constraint for the polarized gluon distribution in the proton of $|\ensuremath{\Delta}g/g({log}_{10}x=\ensuremath{-}{1.6}_{\ensuremath{-}0.4}^{+0.5},\ensuremath{\mu}={m}_{T}^{c}){|}^{2}&lt;0.030$ ($1\ensuremath{\sigma}$) based on a leading-order perturbative quantum chromodynamics model, using the measured asymmetry.

Measurements in Au+Au collisions at sqrt[s_{NN}]=200 GeV of jet correlations for a trigger hadron at intermediate transverse momentum (p_{T,trig}) with associated mesons or baryons at lower p_{T,assoc} indicate strong modification of the away-side jet. The ratio of jet-associated baryons to mesons increases with centrality and p_{T,assoc}. For the most central collisions, the ratio is similar to that for inclusive measurements. This trend is incompatible with in-vacuum fragmentation but could be due to jetlike contributions from correlated soft partons, which recombine upon hadronization.

Quarkonia were predicted to be suppressed in the 'hot' deconfined matter known as the quark gluon plasma (QGP), but they were also seen to suffer from 'cold' nuclear matter effects (parton shadowing, nuclear absorption, etc.). Both at SPS and RHIC, suppression beyond nuclear effects was observed, but the rapidity dependence of the RHIC result is not easy to interpret. I review here the current status of these results, their possible interpretations and the new measurements that could provide insights on quarkonia suppression. Some of them were presented at this conference.

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$γγ$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvertζ_1\rvert$ $\lt$ 2.9 $\times$ 10$^{-13}$ GeV$^{-4}$ and $\lvertζ_2\rvert$ $\lt$ 6.0 $\times$ 10$^{-13}$ GeV$^{-4}$.

The CMS Collaboration has recorded 150μb−1 and 35nb−1 of PbPb and pPb collisions, at 2.76 TeV and 5.02 TeV, respectively. This paper highlights some of the observations made on these samples. A particular emphasis is given to the most recent results regarding collectivity, energy loss, nuclear effects and quarkonium suppression.

A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.

We have developed a silicon pixel detector to enhance the physics capabilities of the PHENIX experiment. This detector, consisting of two layers of sensors, will be installed around the beam pipe at the collision point and covers a pseudo-rapidity of |η| < 1.2 and an azimuth angle of |ϕ| ∼ 2π. The detector uses 200 μm thick silicon sensors and readout chips developed for the ALICE experiment. In order to meet the PHENIX DAQ readout requirements, it is necessary to read out 4 readout chips in parallel. The physics goals of PHENIX require that radiation thickness of the detector be minimized. To meet these criteria, the detector has been designed and developed. In this paper, we report the current status of the development, especially the development of the low-mass readout bus and the front-end readout electronics.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The Silicon Pixel Detector will be installed in summer 2009 as part of the RHIC-PHENIX Silicon Vertex Tracker (VTX) upgrade at the Brookhaven National Laboratory. The VTX consists of a silicon pixel detector and stripixel detector. For the construction of the silicon pixel detector, we have developed a fine pitch and low material readout bus as the backbone parts of the VTX. In this article, we report the development of the readout bus. </para>

This corrects the article DOI: 10.1103/PhysRevLett.109.152301.

Proceedings of the 13th International Conference on Elastic and Diffractive Scattering (Blois Workshop) - Moving Forward into the LHC Era

I present here a concise review of the experimental results obtained at the Relativistic Heavy Ion Collider (RHIC), which shed light on the hot and dense quark gluon matter produced at these high temperature and density conditions.

We report on the creation of a database for quarkonium and open heavy-flavour production in hadronic collisions. This database, made as a collaboration between HepData and the ReteQuarkonii network of the integrating activity I3HP2 of the 7th Framework Programme, provides an up-to-date review on quarkonia and open heavy-flavour existing data. We first present the physics motivation for this project, which is connected to the aim of the ReteQuarkonii network, studies of open heavy-flavour hadrons and quarkonia in nucleus-nucleus collisions. Then we give a general overview of the database and describe the HepData database for particle physics, which is the framework of the quarkonia database. Finally we describe the functionalities of the database with as example the comparison of the production cross section for the J/$ψ$ meson at different energies.

Charged-pion-interferometry measurements were made with respect to the 2$^{\rm nd}$- and 3$^{\rm rd}$-order event plane for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. A strong azimuthal-angle dependence of the extracted Gaussian-source radii was observed with respect to both the 2$^{\rm nd}$- and 3$^{\rm rd}$-order event planes. The results for the 2$^{\rm nd}$-order dependence indicate that the initial eccentricity is reduced during the medium evolution, but not reversed in the final state, which is consistent with previous results. In contrast, the results for the 3$^{\rm rd}$-order dependence indicate that the initial triangular shape is significantly reduced and potentially reversed by the end of the medium evolution, and that the 3$^{\rm rd}$-order oscillations are largely dominated by the dynamical effects from triangular flow.

This note represents an attempt to gather the input related to light-by-light scattering ($\gamma\gamma$) cross-section measurements at LHC with the aim of checking the consistency with different standard model predictions. For the first time, we also consider the contribution from the $\eta_b(1S)$ meson production to the diphoton invariant mass distribution, by calculating its inclusive photoproduction cross-section. Using a simplified set of assumptions, we find a result of $115\pm 19\,\,\text{nb}$, consistent with standard model predictions within two standard deviations. Although an improved determination of the integrated fiducial $\textrm{PbPb}\,(\gamma\gamma)\to \textrm{Pb}^{(\ast)}\textrm{+}\textrm{Pb}^{(\ast)}\,\gamma\gamma$ cross-section by approximately 10\% could be potentially achieved relative to current measurements, further improvements are expected with the inclusion of existing or forthcoming LHC nuclear data.

Interactive shape crafting is an increasingly popular feature in video games, offering players a sense of freedom and personalization. In this work, we propose to combine a stochastic simulation approach to solve the heat equation on Implicit Surface, enabling crafting-ready shapes. Our simulation relies on the "Walk on Sphere" (WoS) approach allowing to solve the asymptotic solution of the heat PDE at any point in space without the need for an explicit mesh structure. To enable interactivity when the shape is moved near a heat source, we propose the integration of time-evolving modifiers. Firstly, using the separation of variables over the PDE enables the approximation of the heating evolution using an additional exponential time variation. Then, we procedurally attach local secondary heat sources to the surface for smooth cool-down. We demonstrate the effectiveness our approach on blended-material shapes generated using CSG operations, combining spatially-varying thermal diffusivity. Overall, our method offers a promising avenue for incorporating often-neglected physical interactions, such as heat-related phenomena, into video games with complex and customizable shapes.

Open charm production in proton-proton collisions represents an important tool to investigate some of the most fundamental aspects of Quantum Chromodynamics, from the partonic mechanisms of heavy-quark production to the process of heavy-quark hadronisation. Over the last decade, the measurement of the production cross sections of charm mesons and baryons in proton-proton (pp) collisions was at the centre of a wide experimental effort at the Large Hadron Collider. Thanks to the complementarity of the different experiments, the production of charm hadrons was measured over a wide transverse momentum region and in different rapidity ranges. In this paper, the measurements of the charm hadrons $D^0$, $D^*$, $D^+$, $D_s^+$, $\Lambda_c^+$ and $\Xi_c^0$ performed by the ALICE, CMS and LHCb collaborations in pp collisions at the centre-of-mass energy $\sqrt{s}=\rm 5.02~TeV$ are combined to determine the total charm-quark production cross section $\sigma_{c\overline{c}}$ in a novel data-driven approach. The resulting total $c\overline{c}$ cross section is \begin{equation*} \begin{aligned} \sigma_\mathrm{c\overline{c}} (\mathrm{pp},5.02\,\mathrm{TeV}) ={} & 8340.9 \pm 217.8\mathrm{ (stat.) } {}^{+367.1}_{-367.2} \mathrm{ (syst.) } {}^{+362.5}_{-457.5} \mathrm{ (extr.) } + 679.9 (\Omega_\mathrm{c})~\mu\mathrm{b}. \end{aligned} \end{equation*} The measured charm-hadron distributions and corresponding cross sections are compared with the most recent theoretical calculations.

Abstract The PHENIX experiment at Relativistic Heavy Ion Collider will be equipped with Silicon Vertex tracker to enhance its physics capability. There are four layers of silicon sensor to reconstruct charged tracks with 50 μ m resolution of decay length measurement. The VTX surrounds the collision point. The inner two layers and the outer two layers are composed of 30 pixel ladders and 44 stripixel ladders, respectively. We have been developing these detectors and done a performance test with 120 GeV proton beam.

Heavy quarkonia production is expected to be sensitive to the formation of a quark gluon plasma (QGP). The PHENIX experiment has measured J/ψ production at $\sqrt{s_{NN}}$ =200 GeV in Au+Au and Cu+Cu collisions, as well as in reference p+p and d+Au runs. J/ψ's were measured both at mid (|y|<0.35) and forward (1.2<|y|<2.2) rapidity. In this letter, we present the A+A preliminary results and compare them to normal cold nuclear matter expectations derived from PHENIX d+Au and p+p measurements as well as to theoretical models including various effects (color screening, recombination, sequential melting...).

A search for long-lived particles (LLPs) produced in association with a Z boson is presented. The study is performed using data from proton-proton collisions with a center-of-mass energy of 13 TeV recorded by the CMS experiment during 2016-2018, corresponding to an integrated luminosity of 117 fb$^{-1}$. The LLPs are assumed to decay to a pair of standard model quarks that are identified as displaced jets within the CMS tracker system. Triggers and selections based on Z boson decays to electron or muon pairs improve the sensitivity to light LLPs (down to 15 GeV). This search provides sensitivity to beyond the standard model scenarios which predict LLPs produced in association with a Z boson. In particular, the results are interpreted in the context of exotic decays of the Higgs boson to a pair of scalar LLPs (H $\to$ SS). The Higgs boson decay branching fraction is constrained to values less than 6% for proper decay lengths of 10-100 mm and for LLP masses between 40 and 55 GeV. In the case of low-mass ($\approx$15 GeV) scalar particles that subsequently decay to a pair of b quarks, the search is sensitive to branching fractions $\mathcal{B}$(H $\to$ SS) $\lt$ 20% for proper decay lengths of 10-50 mm. The use of associated production with a Z boson increases the sensitivity to low-mass LLPs of this analysis with respect to gluon fusion searches. In the case of 15 GeV scalar LLPs, the improvement corresponds to a factor of 2 at a proper decay length of 30 mm.

A measurement of inclusive four-jet production in proton-proton collisions at a center-of-mass energy of 13\TeV is presented. The transverse momenta of jets within $\lvert\eta\rvert \lt$ 4.7 reach down to 35, 30, 25, and 20 GeV for the first-, second-, third-, and fourth-leading jet, respectively. Differential cross sections are measured as functions of the jet transverse momentum, jet pseudorapidity, and several other observables that describe the angular correlations between the jets. The measured distributions show sensitivity to different aspects of the underlying event, parton shower, and matrix element calculations. In particular, the interplay between angular correlations caused by parton shower and double-parton scattering contributions is shown to be important. The double-parton scattering contribution is extracted by means of a template fit to the data, using distributions for single-parton scattering obtained from Monte Carlo event generators and a double-parton scattering distribution constructed from inclusive single-jet events in data. The effective double-parton scattering cross section is calculated and discussed in view of previous measurements and of its dependence on the models used to describe the single-parton scattering background.

The production of electroweak bosons (photons, W and Z particles) in PbPb collisions at a centre-of-mass energy per nucleon pair of 2.76 TeV has been measured with the CMS detector at the LHC. Direct photons are selected by applying isolation criteria, while W and Z bosons are reconstructed through their muonic decay. The production rates in PbPb data are studied as a function of the collision centrality and compared to that in pp interactions (or next-to-leading-order calculations), once normalised by the number of binary nucleon–nucleon interactions. Apart from an expected asymmetry between W+ and W− due to the different quark content of protons and Pb nuclei, no deviation from binary-scaled production is observed. The isolated-photon energy is further used as a reference for away-side jets, which are found to be less energetic in PbPb than in pp collisions.

This note represents an attempt to gather the input related to light-by-light scattering ($\gamma\gamma$) cross-section measurements at LHC with the aim of checking the consistency with different standard model predictions. For the first time, we also consider the contribution from the $\eta_b(1S)$ meson production to the diphoton invariant mass distribution, by calculating its inclusive photoproduction cross-section. Using a simplified set of assumptions, we find a result of $115\pm 19\,\,\text{nb}$, consistent with standard model predictions within two standard deviations. Although an improved determination of the integrated fiducial $\textrm{PbPb}\,(\gamma\gamma)\to \textrm{Pb}^{(\ast)}\textrm{+}\textrm{Pb}^{(\ast)}\,\gamma\gamma$ cross-section by approximately 10\% could be potentially achieved relative to current measurements, further improvements are expected with the inclusion of existing or forthcoming LHC nuclear data.

Le plasma de quarks et de gluons est un état prédit de la matière, dans lequel notre univers devait se trouver pendant les premières microsecondes après le big bang. Des collisions violentes d’ions lourds sont susceptibles de le recréer en laboratoire. De nombreuses signatures de son apparition fugace ont été observées au collisionneur d’ions lourds relativistes (RHIC) de Brookhaven, aux USA, et révèlent les propriétés de cette nouvelle phase de la matière nucléaire.

Heavy quarkonia production is expected to be sensitive to the formation of a quark gluon plasma (QGP). It was (and still is with ongoing data analyses) extensively studied at the CERN SPS, at collision energy $\sqrt{s_{NN}}$ of the order of 20 GeV. An anomalous suppression was clearly observed. The PHENIX experiment at RHIC has presented preliminary results that exhibit a similar amount of $J/ψ$ suppression, at ten times higher collision energy. I review the results obtained at both facilities. While interpreting and comparing them, the importance of understanding normal nuclear effects is emphasized. A new method to derive a reference for Au+Au collisions from the centrality dependence of d+Au measurements at RHIC is exposed.